Photoelectrochemical Methods Development Of Visualization And Identification Of Latent Fingerprints

Latent fingerprints (LFPs) at the scene of a crime are very important clues in forensic investigations because their uniqueness and stableness. Fingerprint detection is for individual identification in terms of their ridge characteristics, such as bifurcation, enclosure, island and ridge ending. However, they are often rarely clear enough to detect, and therefore in forensic practice a different combination or series of "development" treatments are usually required to enhance the visualization. Techniques of fingerprint detection have already developed hundreds of years. Besides the commonly used procedures, such as powder dusting, cyanoacrylate/iodine fuming, ninhydrin staining, there are a large variety of other methods being widely used, e.g., mass spectrometry, infrared spectroscopy, multimetallic deposition, etc. However, they have some apparent drawbacks, e.g., health hazard to the examiners and inevitable destruction of the fingerprint details. Therefore, extending the capability to enhance visualization of latent fingerprints in a simple, rapid, effective and friendly manner is of considerable significance.Firstly, we reported a novel use of aggregation-induced emission (AIE) for recognition of LFPs based on the wet chemistry treatment. AIE compounds are totally opposite to traditional fluorochrome, which are nonluminescent in the soluble state but are induced to emit efficiently after forming aggregates. We explore the possibility of identifying LFPs on glass, stainless steel and aluminium foil on the basis of the AIE effect of tetraphenylethene (TPE) and hexaphenylsilole (HPS). This method was proved to be simple, rapid and user friendly for developing LFPs on wet, nonporous surfaces.Then, we exploited electrochemiluminescence of rubrene to enhance the visualization of latent fingerprints in two different modes by spatially selective lighting up either the bare electrode surface or the fingerprint itself. We studied the influence of electric potential and the rubrene concentration on the imaging quality. Eventually, the method was successful in observing LFPs on conducting substrates, which is simple and efficient in obtaining minutia information.